In vitro analysis of allogeneic lymphocyte interaction. IV. Dual recognition of B cell-associated Mls locus and I-region determinants by a helper allogeneic effect factor (AEF) generated across a minor H locus disparity.

A helper allogeneic effect factor (AEF) was produced across an incompatibility at the minor histocompatibility loci. This AEF is genetically restricted in its activity since it helps B cells only of the stimulator haplotype and of haplotypes that share both an Mls and I-region identity with the stimulator haplotype. The I-region genes involved here map to the I-A and/or I-C subregions. An anti-LyM immunoadsorbent column but neither an anti-H-2 nor an anti-Ia column absorbed AEF helper activity. It is suggested that the activation of T helper cells by a positive allogeneic effect across a minor H locus difference and their genetically restricted interaction with allogeneic B cells may in part be due to the acquisition by alloactivated T cells of stimulator cell-derived LyM and/or Mls determinants. The data presented indicate that helper T cells recognize Mls locus alloantigens in the milieu of self Ia antigens.